7. Use the same style to express related numbers above and below 10. If any of the numbers are above 10, put them all in figures.
We used to have two dogs, one cat and one rabbit. But now we have 5 dogs, 11 cats and 1 rabbit. (The rabbit is male.)
Our four sons consumed a total of 18 hamburgers, 5 bottles of Coke, 12 candy bars, and about 2000 cookies --- all at one sitting, (Figures are used for all the related items of food; the other numbers -- four and one -- are spelled out, because they are not related and are not over 10.)

8. For fast comprehension, numbers in the millions or higher may be expressed as follows:

a. 21 million (in place of 21,000,000)	b. 3 billion ( in place of 3,000,000,000)
c. 14½ million (in place of 14,500.000)	d. 2.4 billion (in place of 2,400,000,000)

This style may be used only when the amount consists of a whole number with nothing more than a simple fraction or decimal following. A number such as 4,832,067 must be written all in figures.
Treat related numbers alike.

Last year we sold 21,557,000 items; this year nearly 23,000,000.
Not: 21,557,000 . . . 23 million.